Apparatus for controlling the tilt of a throttle valve adapted for use in an automotive internal combustion engine by means of an electrical device such as a motor can make possible adjustment of the throttle valve in response not only to the operation of the accelerator pedal in the driver's compartment, but also to various factors, e.g., varying conditions of an engine. Thus, such an apparatus can offer a wide range of application opportunities in designing automotive engines.
One such apparatus for controlling the throttle valve is disclosed by laid-open Japanese Patent Application No. 58-13135 (1983), wherein a throttle valve is connected to a control lever which is in turn connected operatively by way of a reduction gearing to an electric motor, and a spring is provided in such a way to urge the valve toward its "closed" or "throttling" position. The motor, when energized, causes the throttle valve to tilt for controlling the opening of an air passage in which the valve is tiltably mounted. With such an arrangement of the apparatus, in the event of failure of power supply to the motor for any reason, it will be brought to a stop at a position where the supply of power is shut off. Though the spring then acts on the throttle valve to return it to its original position, the motor itself will offer substantial resistance against the action of the return spring. Additional resistance is offered by the reduction gearing which is connected to the valve control lever. In this way, the apparatus according to the prior art has a drawback in that the throttle valve will be substantially locked in its "opened" position if power to the motor is turned off. In other words, the throttle valve should preferably be brought back to its "throttling" position as soon as the motor is de-energized.
In view of the requirement that the throttle valve in operation only has to tilt or turn through an angle of about 90 degrees, an ordinary motor of any known type, if used for tilt adjustment of the valve, will have more component parts than necessary for the desired controlling. An apparatus for controlling the throttle valve designed for use, e.g., in an automobile, is required to operate with a quick response and the motor therefor should preferably be a DC motor. Furthermore, it should be as compact as possible to economize space, and a brushless type is desirable to enable prolonged periods of serviceable life, trouble-free operation and ease of maintenance.